Generally, an ESD protection element is arranged in an integrated circuit in order not that the elements and wiring in the integrated circuit are broken by instantaneous current flowing when the input/output pin of the integrated circuit touches a charged body such as a human body.
The ESD protection element has complicated current-voltage characteristics called snapback characteristics. Accordingly, it is not easy to imitate the operation of the ESD protection element in circuit simulation.
It is assumed to perform circuit simulation with respect to each of a plurality of regions obtained by dividing a characteristic line representing the snapback characteristics. In this case, however, it is difficult to improve the accuracy of operation verification since the boundary position between the regions becomes discontinuous and circuit simulation cannot be performed continuously.